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The controller does not
maintain controller parameters
or parameters are reset each
time the power to the unit is
removed
The controller shows that the
output power is steady but the
process temperature is unstable
The controller alternately heats
for a while then cools
The controller erratically heats
then cools, control is unstable
The bath does not achieve low
temperatures
Service Center (see Authorized Service Centers in Chapter 1) for
assistance.
Note: Before performing the memory check, you need to record the
controller calibration parameters (found in the CAL menu of the
instrument) and any user-adjusted parameters that you have changed
(such as the programmable set points and proportional band).
Memory Check
Doing a memory check is the easiest way to verify the ability of the
battery to maintain controller parameters.
1.
Power off the instrument.
2.
Disconnect the instrument from AC power for 10 seconds.
3.
Reconnect the AC power and power on the instrument.
4.
If the display shows InIT and/or the cycle count shows a low number
such as 0002, the battery is spent and should be replaced. Contact
an Authorized Service Center for assistance.
5.
After replacing the battery, you must reprogram the calibration and
user-adjustable parameters into the controller.
Possible causes are an improper proportional band setting or the fluid
being used.
•
If the bath temperature does not achieve the expected degree of
stability when measured using a thermometer, try adjusting the
proportional band to a narrower width as discussed in Proportional
Band in Chapter 9.
•
Check to ensure the fluid has not deteriorated or is not too thick.
The bath is not stable and the duty cycle is not constant.
The proportional band being too narrow typically causes this oscillation.
Increase the width of the proportional band until the temperature
stabilizes as discussed in Proportional Band in Chapter 9.
If both the bath temperature and output power do not vary periodically
but in a very erratic manner, the problem may be excess noise in the
system. Noise due to the control sensor should be less than 0.001°C.
However, if the probe has been damaged or has developed an
intermittent short, erratic behavior may exist. The probe is located inside
the stirrer motor cover.
•
Check for a damaged probe or poor connection between the probe
and bath.
•
Intermittent shorts in the heater or controller electronic circuitry may
also be a possible cause. Contact an Authorized Service Center
(see Authorized Service Centers in Chapter 1) for assistance.
Too much heating or not enough cooling can cause this problem.
•
Check that the control indicator glows green showing that the
controller is attempting to cool. The heaters may be disabled as a
test by temporarily removing the heater fuses.
•
Insufficient cooling may be caused by lack of refrigerant. Contact an
Authorized Service Center for assistance.
13
Troubleshooting
13-5
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Table of Contents
Troubleshooting
